Why Caribou Choose New Routes Every Year

by Rosamaria Kubny

03/01/2026

Reindeer (caribou). The reindeer is a mammal from the deer family that is perfectly adapted to cold climates. It lives circumpolarly. In summer it roams the tundra; in winter it moves through the taiga of northern Eurasia and North America, as well as Greenland and other Arctic islands. In North America it is known as the caribou. (Photo: Heiner Kubny)

Alaska: Caribou use collective experience to flexibly adapt their migrations to changing winter conditions. This is shown by new long-term studies funded by the U.S. National Science Foundation. The findings provide striking evidence that social memory plays a central role in the survival of large animal herds in a rapidly warming Arctic.

Caribou are the most common large land mammal in the Arctic and a vital food source for many Indigenous communities. At the same time, they undertake the longest seasonal migrations of any land animal, covering several hundred kilometers. Notably, the animals do not follow the same routes every year.

**Reindeer adjust their diet to the seasons. In summer they feed on a wide variety of plants, while in winter they live mainly on reindeer lichens, mosses, and fungi. (Photo: Rosamaria Kubny)**

To understand the causes of this flexibility, a research team led by Eliezer Gurarie, professor at the State University of New York, studied the Western Arctic caribou herd in collaboration with the National Park Service. Over a period of eleven years (2009–2020), more than 300 female animals were tracked using GPS collars. The study area covered about 360,000 square kilometers in northwestern Alaska.

The analysis showed that wintering locations depend largely on weather conditions. In warm, windy winters, caribou more often survived south of the Kobuk River, whereas in snowier, calmer winters, conditions were better north of the river. Each year, the animals decided anew whether to cross the river, apparently based on the herd’s past experiences.

**During seasonal migrations, reindeer gather in large herds that can number several hundred thousand animals regionally. (Photo: Heiner Kubny)**

“A dead animal, by definition, remembers nothing,” says Gurarie. “But the environmental conditions that led to lower survival chances persist in the herd’s collective memory.”

The results show that caribou not only recognize risks but also pass on knowledge socially and use it for collective decision-making. This collective learning reduces the mortality risk for individual animals and increases the survival chances of the entire herd.

Given that the Arctic is warming faster than almost any other region on Earth, this behavior could be crucial for the species’ future. The study demonstrates that social learning processes in wild animals are an underestimated factor in their ability to adapt to climate change.

Rosamaria Kubny, PolarJournal